Plasma Fibrinogen to Platelet Ratio as a Prognostic Factor for Postoperative Recurrence of Esophageal Squamous Cell Carcinoma

Background: Postoperative recurrence of esophageal squamous cell carcinoma is an important factor affecting the survival of patients. Hypercoagulability is a related factor for the recurrence of esophageal squamous cell carcinoma. Fibrinogen/platelet ratio (FPR) is used as a meaningful factor for evaluating coagulation status. The purpose of this study is to evaluate the predictive value of FPR for ESCC postoperative metastasis and its relationship with prognosis. Methods: We collected 607 patients undergoing surgery from 2012 to 2015, and performed clinical analysis, including plasma brinogen count, platelet count, and their ratio, dened as FPR. Follow-up assessment of recurrence and OS, RFS. Results:145 patients (23.8%) experienced postoperative recurrence. There is a correlation between FPR and postoperative metastasis (p <0.001). The area under the curve (AUC) of FPR predicting postoperative recurrence is 0.620 (95% condence interval: 0.554-0.686), which is higher than the single factor AUC value of brinogen and platelets. The overall survival rate (OS) and recurrence-free survival rate (RFS) of patients with higher FPR were signicantly reduced (p = 0.001). Cox regression results show that FPR is an independent predictor of OS and RFS (p=0.004 and <0.028, respectively), while plasma brinogen level is not. The C index of the nomogram model predicting OS and RFS is 0.691 and 0.727, respectively. The calibration curve shows that the predictive ability is basically consistent with the actual observation results. Conclusions: FPR may be a predictor of postoperative recurrence in ESCC patients, and it can predict the prognosis of ESCC patients better than brinogen. are constantly improving, the 5-year survival rate of patients is still poor, and postoperative recurrence is the most important factor for the poor prognosis of patients. Therefore, this study aims to explore whether FPR can early predict postoperative recurrence in patients and its prognostic signicance for OS and RFS. FPR is the ratio of brinogen to platelets, which is more convenient to calculate and can be used to predict the prognosis of gastric cancer. In this study, we combined brinogen and platelets, taking the ratio, to explore the predictive signicance of postoperative ESCC recurrence, as well as the predictive signicance of OS and RFS. We have shown through research that FPR is a good predictor of postoperative ESCC recurrence. Previous studies have shown that brinogen has predictive signicance for postoperative ESCC metastasis. On this basis, we have studied the predictive value of FPR for ESCC postoperative recurrence. Through our data analysis, FPR has a greater predictive value for postoperative recurrence than any single factor of brinogen and platelets. And it shows that FPR is an independent prognostic factor of OS and RFS, while brinogen and platelets are not. This study also established a nomogram to predict the disease-free survival of 3, 5 years and 3, 5 years of overall survival after radical esophagectomy for esophageal cancer, and it can be seen that the calibration curve and the simulation curve t well.


Introduction
Esophageal cancer is one of the most common malignant tumors in the world, and its morbidity and mortality rank seventh and sixth among all tumors [1] . Esophageal cancer can be divided into esophageal squamous cell carcinoma (esophageal squamous cell carcinoma, ESCC) and esophageal adenocarcinoma (EAC). In my country, ESCC is more common, accounting for about 95% of esophageal cancer cases. Although the treatment methods of esophageal cancer continue to improve, according to the data of the National Cancer Center, the ve-year survival rate of esophageal cancer is only 30%.
Postoperative recurrence is the main reason for the poor prognosis. Therefore, it is necessary to further search for effective tumor serum markers. To improve the prognosis. Postoperative metastasis of ESCC occurs most often in lymph nodes, followed by lung, liver, and bone [2] . There are many factors that cause tumor metastasis, including hypercoagulable state and in ammation. There is evidence that in ammation and the coagulation system interact to promote tumor progression [3] . Hyperferricemia is also associated with the poor prognosis of a variety of solid tumors, and compared with non-relapsed cases, relapsed cases have higher brinogen [4] .Thrombocytosis re ects tumor-related in ammation. An increase in platelets [5] and an increase in brinogen indicate a poor prognosis for ESCC [6][7] .
Hyper brinogenemia is closely related to postoperative metastasis of ESCC [8] . In recent years, serum markers for predicting postoperative tumor recurrence have attracted much attention. However, so far there are few applications and clinical applications. Recently, the relationship between hypercoagulability and in ammation and tumor metastasis has attracted much attention. We speculate that the combination of brinogen and platelets can predict postoperative recurrence and prognosis of ESCC better than brinogen or platelets. Therefore, in this study, we collected 607 cases of clinical factors that have predictive signi cance for postoperative metastasis, and evaluated the predictive value of FPR for postoperative recurrence of ESCC and its impact on overall survival and recurrence-free survival.

Collection Of Specimens
Approximately 2ml of venous blood was drawn the morning before the operation when the patient was not eating for the detection of brinogen and platelets, FPR = brinogen/platelets. According to the normal reference range of the cancer hospital, hyper brinogenemia is de ned as: plasma brinogen level is greater than 4.0 g/L; thrombocytosis is de ned as: platelet count greater than 300 × 109/L.

Follow-up
It will be reviewed every 3 months for the rst two years after surgery, every 6 months for the next 3 years, and once a year thereafter. Follow-up methods include telephone follow-up and regular outpatient review (including clinical examination, imaging evaluation, serological examination). Recurrence is de ned as clinical, imaging, or pathological diagnosis to nd a previous local or distant tumor. OS is de ned as the time from surgery to the patient's death from any cause or the last follow-up date when the patient is known to survive. RFS is calculated from the date of surgery to the rst tumor recurrence or death.

Statistical analysis
Chi-square test was used to evaluate the relationship between clinicopathological variables and postoperative recurrence. The receiver operating characteristic (ROC) curve was used to determine the best cut-off values of brinogen, platelets, and FPR, and the predictive value of each variable was evaluated. Kaplan-Meier survival analysis was used to evaluate OS and RFS. Using Cox proportional hazards model, variables with p value < 0.05 in univariate analysis were included in multivariate survival analysis to determine independent prognostic factors. Then select the nomogram for the independent prognostic factors in the COX regression model, and use the R language to calculate it to predict OS and RFS. The 3-year and 5-year prediction probability of the calibration chart is generated by comparing the nomogram, and the prediction accuracy is evaluated by 1000 times of guided resampling. All statistical analyses were performed using SPSS 26.0 software (SPSS, Inc. Chicago, Illinois, USA) and R statistical software. All data p-values < 0.05 are considered statistically signi cant.

Results
The relationship between clinicopathological parameters and postoperative metastasis A total of 607 patients were admitted, of which 145 patients experienced postoperative recurrence, and the remaining 462 patients were assigned to the non-recurrence group. Through ROC curve analysis, the best cut-off values of brinogen, platelets and FPR are 2.94g/L, 233*10[9]/L, 0.01553, respectively. Table 1 shows the relationship between clinicopathological parameters and postoperative recurrence of 607 patients. The results showed that there were signi cant differences in the common clinical characteristics of the two groups in age, tumor differentiation, histological grade, N stage, vascular in ltration, nerve invasion, radiotherapy and chemotherapy, brinogen level and FPR (all p values < 0.05).
There were no signi cant differences in gender, smoking history, drinking history, tumor location and size, T stage, M stage, and platelet level.
The predictive ability of brinogen, platelet and FPR for postoperative recurrence Calculate the AUC values of brinogen, platelets and FPR, and the AUC values are 0.607 0.543-0.671, 0.447 (0.378-0.516), 0.620 (0.554-0.686), respectively, indicating that FPR is better than a single brinogen and platelet count for ESCC surgery The prediction of recurrence is more meaningful ( Table 2 and Fig. 1).

Fpr And Prognosis
The follow-up time for OS and RFS was 60 months. As shown in Fig. 2, compared with the low FPR group, the OS (p = 0.001) and RFS (p < 0.001) of the higher FPR group were worse. Univariate Cox regression analysis (

Prognostic Nomograms Of Os And Rfs
In order to better predict the OS and RFS of ESCC patients, the meaningful single factor factors in the COX review model were selected to establish two nomograms, and the Harrell's c index was used to evaluate the prediction accuracy of the model. The prognostic nomogram of all important independent factors of comprehensive multivariate analysis is shown in Fig. 3. The c index of OS is 0.691, and the C index of RFS is 0.727. As shown in Fig. 4, the calibration curve of the overall survival rate at 3 and 5 years after surgery has a fair t, and the calibration curve for the recurrence-free survival rate at 3 and 5 years after surgery has a good t. The results show that the FPR-based nomogram has a better predictive signi cance for OS and RFS, and the prediction of RFS has a better predictive signi cance for OS.

Discuss
Esophageal cancer is the sixth most deadly tumor in the world. Although the current treatment methods are constantly improving, the 5-year survival rate of patients is still poor, and postoperative recurrence is the most important factor for the poor prognosis of patients. Therefore, this study aims to explore whether FPR can early predict postoperative recurrence in patients and its prognostic signi cance for OS and RFS. FPR is the ratio of brinogen to platelets, which is more convenient to calculate and can be used to predict the prognosis of gastric cancer. In this study, we combined brinogen and platelets, taking the ratio, to explore the predictive signi cance of postoperative ESCC recurrence, as well as the predictive signi cance of OS and RFS. We have shown through research that FPR is a good predictor of postoperative ESCC recurrence. Previous studies have shown that brinogen has predictive signi cance for postoperative ESCC metastasis. On this basis, we have studied the predictive value of FPR for ESCC postoperative recurrence. Through our data analysis, FPR has a greater predictive value for postoperative recurrence than any single factor of brinogen and platelets. And it shows that FPR is an independent prognostic factor of OS and RFS, while brinogen and platelets are not. This study also established a nomogram to predict the disease-free survival of 3, 5 years and 3, 5 years of overall survival after radical esophagectomy for esophageal cancer, and it can be seen that the calibration curve and the simulation curve t well.
There has been no research on FPR in esophageal squamous cell carcinoma. We know a lot of research on platelets and brinogen in tumor metastasis. Tumor metastasis is a multi-system regulation process, in which the blood vasculature plays an important role. Tumor cells fall off from the original site, enter the whole body through the circulatory system, and eventually colonize the target organs, resulting in tumor metastasis. Circulating tumor cells adhere to platelets, leukocytes and endothelial cells to make tumor cells exudate from the vasculature and promote tumor cells to colonize and survive far away [9] . Fibrinogen and platelets are linked to each other and jointly promote the development of tumors. Fibrinogen can promote the adhesion of platelets to tumor cells, and platelets form thrombin so that brinogen accumulates around tumor cells, thereby protecting tumor cells from natural killer cytotoxicity [10] . What mechanism does brinogen mainly promote tumor progression and metastasis? A lot of research is needed in the future. At present, some studies claim that tumors may be the source of brinogen. Fibrinogen, brin and its degradation products have Pro-in ammatory activity, they indirectly stimulate the endothelium to secrete von Willebrand factor, leading to platelet activation associated with neoplastic diseases [11] . Fibrinogen is converted into brin, and brinogen also promotes the formation of new blood vessels, so it can promote tumor growth and metastasis [12] . Fibrinogen levels are elevated in malignant tumors such as gastric cancer, esophageal cancer, breast cancer, lung cancer, colon cancer and ovarian cancer, and high brinogen indicates a poor prognosis. In gastric cancer, brinogen is associated with disease progression and recurrence [13] . In esophageal cancer, it has been reported that brinogen is related to lymph node metastasis and is a biomarker for predicting tumor progression, recurrence and prognosis of esophageal cancer [14] . Thrombocytosis is also closely related to tumor progression. Platelets promote blood clotting associated with cancer. Platelets are recruited to cover the surface of tumor cells, thereby protecting them from immune cell responses and promoting cancer growth and metastasis [15] . There are also reports that cancer cells migrate to the vasculature and interact with platelets, leading to platelet aggregation induced by tumor cells [16] . This shows that tumor cells and platelets have a mutually promoting relationship. Fibrinogen and platelets are elevated in a variety of cancers, such as lung cancer, cervical cancer, stomach cancer, colon cancer, pancreatic cancer, and prostate cancer. In pancreatic cancer, brinogen and platelets can predict tumor metastasis [17] .
Our research shows that FPR's AUC (0.620) is better than the other two indicators, but the AUC value is less than 0.8, which is not high enough, and more data in the future are needed for the next step of veri cation. The limitations of this study include that this is a retrospective study, the data comes from a single organization, the sample size of the data is small, and the sample size needs to be increased to verify the accuracy of the FPR cutoff value and its impact on the prognosis. Secondly, the risk model we evaluated also comes from a single institution, and its applicability is relatively limited, and further multiinstitution research is needed. In summary, preoperative FPR is convenient, cheap, and simple to calculate. It can predict postoperative recurrence of ESCC patients better than plasma brinogen levels.
Patients with high preoperative FPR are more likely to relapse after surgery, and have poor OS and RFS.
Potential limitations of this study include the use of a retrospective design. In order to select a more uniform patient background, we only included patients with esophageal cancer who were likely to be Page 7/12 cured by surgery, and excluded patients with esophageal cancer who received neoadjuvant therapy, which may also limit the general application of the results of the study. In addition, larger-scale prospective studies are needed to con rm these preliminary results.

Declarations
Authors' contributions GLY was involved in data analysis, interpretation and manuscript writing. GLY and YQX were involved in collection data. ZJY and SMX was involved in conception and design. All authors contributed to the article and approved the nal manuscript.

Funding
The authors received no speci c funding for this study.

Availability of data and materials
The datasets in this study is available by request from the corresponding author. For more information, please contact the corresponding author.
Ethics approval and consent to participate All the procedures followed were in accordance with the ethical guidelines of the Helsinki Declaration. The study protocol was approved by the Medical Ethical Committee of in the A liated Tumor Hospital of Nantong University. All patients were given informed written consent. And We received written consent from all patients.

Consent for publication
Not applicable.
Competing interests Figure 1 The receiver operating characteristic (ROC) curves of Platelet, Fibrinogen and FPR for predicting recurrence. The area under the ROC curve (AUC) was 0.447 and 0.607 for Platelet, Fibrinogen, respectively. The AUC increased to 0.620 for the FPR.

Figure 2
Kaplan-Meier analysis of preoperative FPR level in 607 patients with esophageal squamous cell carcinoma.FPR was signi cantly associated with overall survival(a) and recurrence-free survival(b).

Figure 3
Nomograms for predicting risk of 3-y and 5-y overall survival (a) and recurrence-free survival (b) in surgical patients with esophageal squamous cell carcinoma.The units of length and width are centimeters (cm).